Audiovisual data transmission system and audiovisual data transmission method

ABSTRACT

An audiovisual data transmission system includes the following components. A filesystem module creates a file that contains at least one of video data and audio data stored in a storage unit. A conversion processing unit manages a file created by the filesystem module. A filesystem-in-userspace module provides an interface between the conversion processing unit and the filesystem module. An update detecting unit detects an update of at least one of video data and audio data contained in a file. In response to an instruction to acquire a file managed by the conversion processing unit received in a state where an update of the file is detected by the update detecting unit, a server makes an inquiry to the conversion processing unit and repeatedly performs a read process in which the file is read, via the filesystem-in-userspace module.

BACKGROUND

The present disclosure relates to an audiovisual data transmissionsystem and an audiovisual data transmission method for transmitting atleast one of video data and audio data (hereinafter, referred to as “AVdata”) accumulated in storage.

AV data accumulated in storage is managed by a filesystem on a“file-by-file” basis. Most operating systems (hereinafter, abbreviatedas “OS”) include a filesystem as a standard tool thereof. Thus, afilesystem included in an OS as a standard tool is generally used.

When AV data of each file accumulated in storage is read, a protocol forfile transfer which is compliant with the filesystem is used. As theprotocol for file transfer, for example, a protocol called file transferprotocol (FTP) is often used. FTP is defined as an application-layerprotocol that uses transmission control protocol (TCP), which is widelyused for transferring data over the Internet or the like.

When an AV data reproducing apparatus reads AV data accumulated instorage by using FTP, the AV data reproducing apparatus serves as an FTPclient, whereas a controller of the storage serves as an FTP server. TheFTP client requests the FTP server to acquire a file containing desiredAV data. The FTP server reads the AV data of the file specified by theFTP client from the storage, and transfers the read AV data to the FTPclient.

SUMMARY

FTP is a common protocol for file transfer. The use of FTP as thetransfer protocol allows a server to transfer AV data to variousdevices. Generally, data that is to undergo FTP-based transmission has adetermined file size. Accordingly, it is difficult to transmit AV dataof live video that is being captured by a camcorder, by using FTPwithout any additional measures. Specifically, AV data of live video iscontinuously accumulated in storage until broadcasting thereof ends. Ifthe client instructs the server to acquire AV data of the live video byusing FTP at a specific time point, the AV data that has beenaccumulated in the storage of the server up to that specific time pointis transferred but the AV data of the live video captured after thespecific time point is not acquirable without any additional measures.

In order to transmit AV data having a non-determined file size, such asAV data of live video, a dedicated protocol different from FTP and adedicated filesystem are often used. Japanese Unexamined PatentApplication Publication No. 9-319523 discloses a dedicated filesystemsuitably used for AV data.

However, preparation of a dedicated filesystem for transmission of AVdata involves allocation of a module, which executes the dedicatedfilesystem, in the kernel space of the operating system, which executesan AV data transmission process. However, this is not preferable becausethe system configuration becomes more complicated.

Accordingly, it is desirable to easily transmit AV data having anon-determined size, such as AV data of live video, by using a protocolfor AV data having a determined file size.

An embodiment of the present disclosure is applied to an audiovisualdata transmission system including a filesystem module, a conversionprocessing unit, a filesystem-in-userspace module, an update detectingunit, and a server. The filesystem module creates a file that containsat least one of video data and audio data stored in a storage unit. Theconversion processing unit manages a file created by the filesystemmodule. The filesystem-in-userspace module provides an interface betweenthe conversion processing unit and the filesystem module. The updatedetecting unit detects an update of at least one of video data and audiodata contained in a file.

In response to an instruction to acquire a file managed by theconversion processing unit received in a state where an update of thefile is detected by the update detecting unit, the server makes aninquiry to the conversion processing unit via thefilesystem-in-userspace module and repeatedly performs a read process inwhich the file is read via the filesystem-in-userspace module.

An audiovisual data transmission method according to an embodiment ofthe present disclosure includes 1) creating a file that contains atleast one of video data and audio data stored in a storage unit, 2)managing a file created in the creating of a file, 3) providing aninterface between a management process performed in the managing of afile and a file creation process performed in the creating of a file, ina kernel space of an operating system, 4) detecting an update of atleast one of video data and audio data contained in a file, and 5) inresponse to an instruction to acquire a file managed in the managing ofa file received in a state where an update of the file is detected inthe detecting of an update, making an inquiry to the managing of a filevia the interface provided in the providing of an interface, andrepeatedly performing a read process in which the file is read via thefilesystem-in-userspace module.

According to the embodiments of the present disclosure, the server makesan inquiry to the conversion processing unit via thefilesystem-in-userspace module and performs a file read process via thefilesystem-in-userspace module. Thus, the conversion processing unitthat performs a process of reading AV data having a variable file sizeis allocated in the user space of the operating system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an example of a configuration ofan AV data transmission system according to an embodiment of the presentdisclosure;

FIG. 2 is a block diagram illustrating an example of a configuration ofan AV data recording-reproducing apparatus according to an embodiment ofthe present disclosure;

FIG. 3 is a sequence diagram illustrating a procedure of reading dataaccording to an embodiment of the present disclosure;

FIG. 4 is a flowchart illustrating a process of reading data accordingto an embodiment of the present disclosure; and

FIG. 5 is an explanatory diagram illustrating an example of an operationof reading data according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Examples of an AV data transmission system and an AV data transmissionmethod according to embodiments of the present disclosure will bedescribed below with reference to the accompanying drawings in the orderas follows:

1. Example of configuration of entire system (FIG. 1),2. Example of configuration for reading virtual file (FIG. 2),3. Example of procedure of read operation (FIGS. 3 and 4), and4. Example of specific read operation (FIG. 5).It should be noted that the present disclosure is not limited to theexamples below.

1. Example of Configuration of Entire System

FIG. 1 is a block diagram illustrating an example of a configuration ofan AV data transmission system according to an embodiment of the presentdisclosure.

An AV data recording-reproducing apparatus 1 included in the AV datatransmission system according to the embodiment of the presentdisclosure includes storage 20 in which AV data is recorded. The AV dataincludes video data and audio data. A controller 10, which is includedin the AV data recording-reproducing apparatus 1, controls recording ofAV data in the storage 20 and reproduction of the AV data. In thecontroller 10, software of the operation system (OS) that controls thestorage 20 is implemented. The OS has the kernel space and the userspace. The kernel space is a layer in which hardware, such as thestorage 20, is driven. The user space is a layer in which applicationprograms are executed.

When the controller 10 executes a process of recording AV data in thestorage 20 and a process of reproducing the AV data, the controller 10uses a cache memory 31, which is included in the AV datarecording-reproducing apparatus 1, to temporarily store the AV data.

The AV data recording-reproducing apparatus 1 also includes a recordingprocessing unit 32, a reproduction processing unit 33, and an FTP server34. Under control of the controller 10, the recording processing unit 32records AV data input from a camera 40 or the like in the storage 20.Under control of the controller 10, the reproduction processing unit 33supplies a monitor 50 with AV data read from the storage 20. The FTPserver 34 transfers AV data read from the storage 20, as a file, to acomputer 60 by using FTP. The computer 60, for example, edits thesupplied AV data. A file to be transferred from the FTP server 34 to thecomputer 60 is a virtual file created by a virtual filesystem module,which will be described later. Data to be transferred from the FTPserver 34 to the computer 60 may be constituted by one of video data andaudio data. Additionally, AV data to be transferred as a file may beattached with metadata, which is additional data of the AV data.

2. Example of Configuration for Reading Virtual File

Next, a configuration in the AV data recording-reproducing apparatus 1will be described, the configuration being used when the FTP server 34transfers AV data recorded in the storage 20 to the computer 60. In FIG.2, the computer 60 is illustrated as an FTP client 61 that receives afile by using FTP.

As illustrated in FIG. 2, the AV data recording-reproducing apparatus 1includes an optical disc 21, a memory card 22, and a solid state drive(SSD) 23 as the storage 20 that stores AV data. The SSD 23 is a massstorage device realized with a flash memory. The optical disc 21 and thememory card 22 are removable from the AV data recording-reproducingapparatus 1. The SSD 23 may be fixed in the AV datarecording-reproducing apparatus 1 or may be removable from the AV datarecording-reproducing apparatus 1. Although the AV datarecording-reproducing apparatus 1 illustrated in FIG. 2 includes all theoptical disc 21, the memory card 22, and the SSD 23, the AV datarecording-reproducing apparatus 1 may include any one of them.Alternatively, the AV data recording-reproducing apparatus 1 may includestorage of other kinds, such as a hard disk drive (HDD).

In the following description, the optical disc 21, the memory card 22,and the SSD 23 are collectively referred to as storage devices whendistinction therebetween is not desired.

The AV data recording-reproducing apparatus 1 also includes a virtualfilesystem module 11. Data transfer is performed between the virtualfilesystem module 11 and the storage devices 21, 22, and 23 viafilesystem modules 17, 18, 19 for the storage devices 21, 22, and 23,respectively. Specifically, data transfer is performed between theoptical disc 21 and the virtual filesystem module 11 via the discfilesystem module 17. Data transfer is performed between the memory card22 and the virtual filesystem module 11 via the memory-card filesystemmodule 18. Data transfer is performed between the SSD 23 and the virtualfilesystem module 11 via the SSD filesystem module 19.

The virtual filesystem module 11 is allocated in the kernel space of theoperating system implemented in the AV data recording-reproducingapparatus 1.

The virtual filesystem module 11 creates virtual files containing datastored by the storage devices 21, 22, and 23. The virtual files arefiles having a format in which data stored in the storage devices 21,22, and 23 is read by the FTP server 34 using FTP. In order to acquirethe virtual files, the AV data recording-reproducing apparatus 1includes a conversion-processing-unit interface (I/F) 12 and aconversion processing unit 13. The conversion processing unit 13performs a conversion process so as to handle data stored in the storagedevices 21, 22, and 23 as data contained in virtual files. Theconversion-processing-unit interface 12 serves as an interface betweenthe conversion processing unit 13 and a filesystem-in-userspace (FUSE)module 16, which will be described later.

The conversion-processing-unit interface 12 manages a session in whichthe FTP server 34 reads a virtual file. The conversion processing unit13 communicates, via a divining-joining processing unit 14, with thestorage devices 21, 22, and 23 connected to the virtual filesystemmodule 11. Through this communication, the conversion processing unit 13integrates pieces of AV data separately recorded in the storage devices21, 22, and 23 into data of one file. The conversion-processing-unitinterface 12 and the conversion processing unit 13 are allocated in theuser space of the operating system implemented in the AV datarecording-reproducing apparatus 1.

The virtual filesystem module 11 is connected to an ongoing-updatedetecting unit 15. The ongoing-update detecting unit 15 detects that AVdata contained in a virtual file created by the virtual filesystemmodule 11 is being updated. A state where AV data is being updated is astate where AV data is being newly recorded in the storage device 21,22, or 23. The ongoing-update detecting unit 15 and the dividing-joiningprocessing unit 14 are also allocated in the user space.

Furthermore, the AV data recording-reproducing apparatus 1 includes theFUSE module 16 that provides an interface between the virtual filesystemmodule 11 and the conversion-processing-unit interface 12 during filetransfer. The FUSE module 16 is allocated in the kernel space, andserves as an interface between the kernel space and theconversion-processing-unit interface 12 allocated in the user space.Inclusion of the FUSE module 16 allows the conversion-processing-unitinterface 12 and the conversion processing unit 13 to execute uniquefunctions related to virtual files without any modifications of thekernel code handled by the virtual filesystem module 11. Functions thatthe conversion-processing-unit interface 12 and the conversionprocessing unit 13 are able to execute via the FUSE module 16 will bedescribed later.

The FTP server 34 transfers a virtual file read from the virtualfilesystem module 11, to the FTP client 61 by using FTP.

3. Example of Procedure of Read Operation (FIGS. 3 and 4)

Next, with reference to FIGS. 3 and 4, a description will be given of aprocedure of reading AV data stored in the storage 20 when the FTPserver 34 transfers the AV data to the FTP client 61 by using FTP. Inthis example, it is assumed that AV data stored in the storage device(SSD) 23 is read. This process is similarly used when AV data is readfrom the other storage devices 21 and 22.

FIG. 3 is a sequence diagram illustrating a procedure of a readoperation.

First, as illustrated in FIG. 3, the FTP client 61 instructs the FTPserver 34 to acquire a file (step S11). The FTP server 34 havingreceived this instruction executes a system call “open” for opening thespecified file, on the FUSE module 16 (step S12). The FUSE module 16having been invoked by the system call “open” then sends a command“open” to the conversion-processing-unit interface 12 (step S13).

The conversion-processing-unit interface 12 performs a lookup process inwhich information about the virtual file specified in the command “open”is read (step S14). Then, the conversion-processing-unit interface 12allocates a session table into which data is to be read from the storagedevice 23 (step S15). At this time, information, such as the size of thevirtual file specified in the command “open” and the creation time ofthe file, is stored in the allocated session table. Here, the size ofthe virtual file is an amount of AV data contained in the virtual file.

The conversion-processing-unit interface 12 having allocated the sessiontable then sends a command “open” to the conversion processing unit 13(step S16). The conversion processing unit 13 having received thecommand “open” prepares for reading of the specified file. Subsequently,the conversion processing unit 13 returns a command “open return” to theconversion-processing-unit interface 12 (step S17).

The conversion-processing-unit interface 12 having received the command“open return” then sends a command “return” to the FTP server 34 via theFUSE module 16 (steps S18 and S19).

Next, the FTP server 34 having received the command “return” executes asystem call “fstat” on the FUSE module 16 in order to acquireinformation, such as the file size (step S20). The FUSE module 16 havingbeen invoked by the system call “fstat” sends a command “getattr” to theconversion-processing-unit interface 12 (step S21). Theconversion-processing-unit interface 12 performs the lookup process onthe session table (step S22). In this lookup process, the size of thevirtual file held in the session table is read. Subsequently, theconversion-processing-unit interface 12 attaches the read size of thevirtual file to the command “return”, and sends the command “return” tothe FTP server 34 (steps S23 and S24). The FTP server 34 stores thereceived size of the virtual file therein.

Then, the FTP server 34 executes a system call “sendfile” on the FUSEmodule 16 in order to makes a request for transfer of the file havingthe acquired file size (step S25). The FUSE module 16 having beeninvoked by the system call “sendfile” sends a command “read” to theconversion-processing-unit interface 12 (step S26). Theconversion-processing-unit interface 12 having received this command“read” updates the size held in the session table (step S27). Here, theconversion-processing-unit interface 12 updates the size upon receipt ofthe first command “read” immediately after receipt of the command“open”.

Also, the conversion processing unit 13 sends a command “open” to thedivining-joining processing unit 14 (step S28).

Subsequently, the conversion-processing-unit interface 12 havingreceived the command “read” in step S27 sends a command “read” to theconversion processing unit 13 (step S29). The conversion processing unit13 having received the command “read” then sends a command “read” to thestorage device 23 via the divining-joining processing unit 14 (steps S30and S31).

The storage device 23 having received the command “read” sends thespecified AV data to the divining-joining processing unit 14 (step S32).The divining-joining processing unit 14 may join (or divide) the AVdata. Then, the divining-joining processing unit 14 sends the AV data tothe conversion processing unit 13 (step S33).

The conversion processing unit 13 sends the supplied AV data to theconversion-processing-unit interface 12 (step S34). Subsequently, theconversion-processing-unit interface 12 sends, as a file regarding aresponse “return” to the command “read” sent in step S26, the acquiredAV data to the FUSE module 16 (step S35). The FUSE module 16 then sendsthe AV data of the supplied file to the FTP client 61 via the FTP server34 (step S36).

If an amount of data acquired by the FUSE module 16 in step S35 has notreached the size of the file specified by the read command, the FUSEmodule 16 repeatedly sends the command “read” to theconversion-processing-unit interface 12.

In the example illustrated in FIG. 3, it is assumed that the commands“read” are sent from the FUSE module 16 to the storage device 23sequentially in steps S37, S38, S39, and S40 after such reading of datais performed multiple times. The data read from the storage device 23 inresponse to these commands is sent to the conversion-processing-unitinterface 12 in steps S41, S42, and S43. Then, theconversion-processing-unit interface 12 determines that reading of datahaving the file size held in the session table has been completed in thelookup process (step S44). The AV data supplied to theconversion-processing-unit interface 12 is sent to the FTP client 61 viathe FUSE module 16 and the FTP server 34 (steps S45 and S46). Also, theFUSE module 16 sends the command “return” to the FTP server 34 (stepS47). This command “return” indicates that file transfer requested bythe command “sendfile” sent in step S25 has been completed.

When it is determined in step S44 that reading of data having the filesize held in the session table has been completed, theconversion-processing-unit interface 12 waits for a predetermined timeand then updates the size held in the session table. The waiting and theupdate of the size are performed only when the ongoing-update detectingunit 15 (FIG. 2) detects that an update is in progress, and are notperformed when the update is not underway.

Subsequently, the FTP server 34 having received the command “return” instep S47 executes the system call “fstat” on the FUSE module 16 in orderacquire the file size (step S48). The FUSE module 16 having been invokedby the system call “fstat” sends the command “getattr” to theconversion-processing-unit interface 12 (step 49). Theconversion-processing-unit interface 12 then performs the lookup processon the session table (step S50). In this lookup process, the size of thevirtual file held in the session table is read. Then, theconversion-processing-unit interface 12 attaches the read size of thevirtual file to the command “return”, and returns the command “return”to the FTP server 34 (steps S51 and S52). The FTP server 34 determineswhether or not the received size of the virtual file matches the filesize that the FTP server 34 has been notified of in step S24.

If the file sizes match, the FTP server 34 determines that reading ofthe virtual file has been completed. The FTP server 34 thus performs aread termination process in step S53 and in the following steps, whichwill be described later. If the file sizes do not match, the FTP server34 determines that there is data that has not been read. The processreturns to step S25, in which the FTP server 34 executes on the FUSEmodule 16 the system call “sendfile”, with which a request for transferof the file having the file size is made.

If the FTP server 34 determines that reading of the virtual file hasbeen completed, the FTP server 34 executes a system call “close” on theFUSE module 16 (step S53). The FUSE module 16 having been invoked by thesystem call “close” sends a command “close” to the conversion processingunit 13 via the conversion-processing-unit interface 12 (steps S54 andS55). A command “close” is also sent to the dividing-joining processingunit 14 from the conversion processing unit 13 (step S56).

The conversion processing unit 13 having received the command “close”sent in step S55 sends a response command “close return” to theconversion-processing-unit interface 12 (step S57). Theconversion-processing-unit interface 12 having received this commandsends a response command “return” to the FTP server 34 via the FUSEmodule 16 (steps S58 and S59).

The FTP server 34 having determined that reading of this file has beencompleted sends “return message” to the FTP client 61, therebyterminating the file transfer performed by using FTP commands (stepS60).

A flowchart of FIG. 4 is a diagram illustrating the state transitionillustrated in FIG. 3 as a flow of contents of processes. FIG. 4illustrates contents of processes performed by the FTP server 34, theFUSE module 16, the conversion-processing-unit interface 12, and theconversion processing unit 13. In this case, the processes performed bythe FTP server 34 and the FUSE module 16 are collectively illustrated asone flow.

First, the FTP server 34 determines whether or not a request foracquisition of a file is made by the FTP client 61 (step S101). Upondetermining that a request for acquisition of a file is made, the FTPserver 34 instructs the conversion-processing-unit interface 12 to openthe file (step S102).

The conversion-processing-unit interface 12 having received this fileopen instruction allocates a session table (step S201). Here, theconversion-processing-unit interface 12 determines whether or not thesize of the specified file is zero (step S202). If the size of the fileis zero, the conversion-processing-unit interface 12 waits until thesize of the file is updated from zero (step S203).

If it is determined in step S202 that the size is not zero, or if thesize is updated in step S203, the conversion-processing-unit interface12 stores data, such as the size and creation time of the specifiedfile, in the session table (step S204). Thereafter, theconversion-processing-unit interface 12 instructs the conversionprocessing unit 13 to open AV data (step S205). The conversionprocessing unit 13 having received this instruction performs a processof opening a file containing the specified AV data (step S301).

Further, the FTP server 34 instructs the conversion-processing-unitinterface 12 to acquire the size of the file (step S103). In response tothe instruction, the conversion-processing-unit interface 12 returns thesize of the file (step S206).

Thereafter, the FTP server 34 makes a file transfer request by using theacquired file size (step S104). The conversion-processing-unit interface12 having received this transfer request updates the size held in thesession table (step S207), and makes a read request for reading of AVdata to the conversion processing unit 13 (step S208).

The conversion processing unit 13 having received this read requeststarts transferring the AV data (step S302). The transferred AV data isthen transferred to the FTP server 34. The AV data transferred to theFTP server 34 is further transferred to the FTP client 61 (step S105).

After the transfer of the AV data is started, theconversion-processing-unit interface 12 determines whether or notreading of effective data has been finished (step S209). If theconversion-processing-unit interface 12 determines that reading ofeffective data has been finished, the conversion-processing-unitinterface 12 waits for a predetermined period until the file size of theAV data is updated. After the file size is updated, theconversion-processing-unit interface 12 updates the size held in thesession table (step S210). If there is no update of the file size evenafter the predetermined period, the conversion-processing-unit interface12 determines that reading of the AV data has been finished.

Thereafter, the FTP server 34 instructs the conversion-processing-unitinterface 12 to acquire the size of the file (step S106). In response tothe instruction, the conversion-processing-unit interface 12 returns thesize of the file (step S211). The FTP server 34 then determines whetheror not the file size sent in step S206 matches the file size sent instep S211 (step S107). If the file sizes do not match, the processreturns to step S104, in which the FTP server 34 makes a request fortransfer of not-yet-read data among the data having the updated filesize.

If the file sizes match in step S107, the FTP server 34 instructs theconversion-processing-unit interface 12 to close the file (step S108).The conversion-processing-unit interface 12 having received this closeinstruction performs a file close process (step S212). Then, theconversion processing unit 13 performs a close process on the file inwhich the AV data is recorded (step S303).

Subsequently, the FTP server 34 instructs the FTP client 61 to terminatethe file transfer (step S109).

4. Example of Specific Read Operation

Next, an example of a specific AV data transfer state will be describedwith reference to FIG. 5.

The example illustrated in FIG. 5 corresponds to a case where AV dataobtained by shooting a scene using the camera 40 is recorded in storageincluded in the FTP server 34 and the AV data recorded in the storage istransferred to the FTP client 61.

First, at a time T11, the camera 40 starts shooting a scene. AV dataresulting from the shooting by the camera 40 is transferred to thestorage included in the FTP server 34, whereby recording of the AV datais started. At this time, the size of a file that contains the AV datais changed from zero to an amount of recorded data, and, for example,the recording start time is attached to the file, in the FTP server 34.

At a time T12, at which a predetermined time has passed from the startof shooting, the FTP client 61 makes an acquisition request foracquisition of the file containing the AV data resulting from theshooting by the camera 40, to the FTP server 34. It is assumed that thefile size of the AV data accumulated in the storage at the time when theFTP server 34 has received this acquisition request is a size X1.

At this time, the FTP server 34 notifies the FTP client 61 of the filesize X1. Then, transfer of the AV data having the file size X1 from theFTP server 34 to the FTP client 61 is started. Here, the FTP server 34detects that the file of the AV data is being updated.

As a result of transfer of the AV data to the FTP client 61 in thismanner, the FTP client 61 completes acquisition of the AV data havingthe size X1 at a time T13. At the time T13, the file size has beenupdated to a size X2. Accordingly, the FTP server 34 detects that thefile size X1 acquired at the start of the file transfer does not matchthe current file size X2. Once the FTP server 34 detects that the filesizes X1 and X2 do not match, reading of not-yet-transferred AV data(data corresponding to a difference between the sizes X2 and X1) isstarted. In this way, the FTP client 61 starts acquiring the datacorresponding to the difference between the file sizes X2 and X1.

It is assumed that shooting by the camera 40 ends at a time T14 and theFTP server 34 no longer detects that the update is in progress. It isalso assumed that the file size at the end of the shooting is a size X3.

At a time T15 which is after the time T14, the FTP client 61 completesacquisition of the AV data having the size X2. At the time T15, the filesize has been updated to the size X3 in the FTP server 34. Accordingly,the FTP server 34 detects that the file size X2 of the already-read filedoes not match the current file size X3. Once the FTP server 34 detectsthat the file sizes X2 and X3 do not match, reading ofnot-yet-transferred AV data (data corresponding to a difference betweenthe sizes X3 and X2) is started. In this way, the FTP client 61 startsacquiring the data corresponding to the difference between the sizes X3and X2.

If the FTP server 34 completes transfer of the data corresponding to thedifference between the sizes X3 and X2 at a time T16, the FTP clientcompletes acquisition of the entire AV data (data having the size X3).At the time T16, both the file size of the already-transferred file andthe file size of the file stored in the storage are equal to X3, i.e.,match, in the FTP server 34. Thus, a file-transfer termination process,such as closing of the file, is performed.

As described above, even if the size of AV data accumulated in storagevaries, the entire AV data may be transferred to the FTP client 61 byusing FTP. Accordingly, AV data having a variable data size, such as AVdata of live video, may be easily read by using a FTP-based filetransfer function of an apparatus that functions as the FTP client 61.

In this case, a process of transferring data having a variable size isperformed in the FTP server 34 on the basis of comparison between thefile size held by the conversion-processing-unit interface 12, which isallocated in the user space of the AV data recording-reproducingapparatus 1, and the file size held by the FTP server 34. When theconversion-processing-unit interface 12 and the FTP server 34 performthis comparison between the file sizes, they communicate with each othervia the FUSE module 16 which is prepared in the kernel space. Thus, acontrol process for continuously reading a file that has a variable sizemay be performed in the conversion-processing-unit interface 12 and theconversion processing unit 13, which are allocated in the user space. Asa result, no modification is made in the kernel space in order to allowthe AV data recording-reproducing apparatus 1 according to theembodiment of the present disclosure to continuously read a file havinga variable size, compared with a general apparatus that performs filetransfer by using FTP.

It is easier to modify modules allocated in the user space than thoseallocated in the kernel space. Thus, it is relatively easy to configurethe conversion-processing-unit interface 12 and the conversionprocessing unit 13, which are allocated in the user space, so that theyperform a process of continuously reading a file having a variable sizeas in the embodiments of the present disclosure.

Since the conversion-processing-unit interface 12 and the FTP server 34perform the comparison between the file sizes at the start and end ofreading, whether or not reading is to be continued may be determined byperforming the comparison the minimum number of times.

If the file size acquired at the start of reading matches the file sizeacquired at the end of reading, the conversion-processing-unit interface12 waits until the file size is updated. With this configuration, a casemay be handled in which reading of data from the storage is performedfaster than writing of data in the storage. Additionally, theconversion-processing-unit interface 12 waits until the file size isupdated in step S44 illustrated in FIG. 3 only when the ongoing-updatedetecting unit 15 (FIG. 2) detects that the file is being updated.Accordingly, the time taken for reading does not increase when datahaving a determined file size is transferred by using FTP.

In the above-described examples according to the embodiments, the casehas been described in which file transfer is performed by using FTP.However, the file transfer is not limited to that based on the FTP, andvarious protocols for file transfer may be adopted.

Additionally, although virtual files are used as files to betransferred, files other than virtual files may be used.

The present disclosure may take configurations as follows:

1) An audiovisual data transmission system including:

a filesystem module configured to create a file that contains at leastone of video data and audio data stored in a storage unit;

a conversion processing unit configured to manage a file created by thefilesystem module;

a filesystem-in-userspace module configured to provide an interfacebetween the conversion processing unit and the filesystem module;

an update detecting unit configured to detect an update of at least oneof video data and audio data contained in a file; and

a server configured to, in response to an instruction to acquire a filemanaged by the conversion processing unit received in a state where anupdate of the file is detected by the update detecting unit, make aninquiry to the conversion processing unit via thefilesystem-in-userspace module and repeatedly perform a read process inwhich the file is read via the filesystem-in-userspace module.

2) The audiovisual data transmission system according to 1),

wherein the filesystem-in-userspace module is allocated in a kernelspace of an operating system, and

wherein the conversion processing unit is allocated in a user space ofthe operating system.

3) The audiovisual data transmission system according to 1) or 2),wherein the filesystem module creates a file to be transferred using thefile transfer protocol.

4) The audiovisual data transmission system according to any one of 1)to 3),

wherein the server makes an inquiry regarding the size of the file tothe conversion processing unit at least at the start and end of a readprocess in which the file is read, and

wherein when the size obtained at the start does not match the sizeobtained at the end, the server continuously performs the read process.

5) The audiovisual data transmission system according to 4), whereinwhen the size obtained at the start matches the size obtained at theend, the server waits until the size of the file is updated.

6) An audiovisual data transmission method including:

creating a file that contains at least one of video data and audio datastored in a storage unit;

managing a file created in the creating of a file;

providing an interface between a management process performed in themanaging of a file and a file creation process performed in the creatingof a file, in a kernel space of an operating system;

detecting an update of at least one of video data and audio datacontained in a file; and

in response to an instruction to acquire a file managed in the managingof a file in a state where an update of the file is detected in thedetecting of an update, making an inquiry to the managing of a file viathe interface provided in the providing of an interface, and repeatedlyperforming a read process in which the file is read via thefilesystem-in-userspace module.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. An audiovisual data transmission systemcomprising: a filesystem module configured to create a file thatcontains at least one of video data and audio data stored in a storageunit; a conversion processing unit configured to manage a file createdby the filesystem module; a filesystem-in-userspace module configured toprovide an interface between the conversion processing unit and thefilesystem module; an update detecting unit configured to detect anupdate of at least one of video data and audio data contained in a file;and a server configured to, in response to an instruction to acquire afile managed by the conversion processing unit received in a state wherean update of the file is detected by the update detecting unit, make aninquiry to the conversion processing unit via thefilesystem-in-userspace module and repeatedly perform a read process inwhich the file is read via the filesystem-in-userspace module.
 2. Theaudiovisual data transmission system according to claim 1, wherein thefilesystem-in-userspace module is allocated in a kernel space of anoperating system, and wherein the conversion processing unit isallocated in a user space of the operating system.
 3. The audiovisualdata transmission system according to claim 1, wherein the filesystemmodule creates a file to be transferred using the file transferprotocol.
 4. The audiovisual data transmission system according to claim1, wherein the server makes an inquiry regarding the size of the file tothe conversion processing unit at least at the start and end of a readprocess in which the file is read, and wherein when the size obtained atthe start does not match the size obtained at the end, the servercontinuously performs the read process.
 5. The audiovisual datatransmission system according to claim 4, wherein when the size obtainedat the start matches the size obtained at the end, the server waitsuntil the size of the file is updated.
 6. An audiovisual datatransmission method comprising: creating a file that contains at leastone of video data and audio data stored in a storage unit; managing afile created in the creating of a file; providing an interface between amanagement process performed in the managing of a file and a filecreation process performed in the creating of a file, in a kernel spaceof an operating system; detecting an update of at least one of videodata and audio data contained in a file; and in response to aninstruction to acquire a file managed in the managing of a file in astate where an update of the file is detected in the detecting of anupdate, making an inquiry to the managing of a file via the interfaceprovided in the providing of an interface, and repeatedly performing aread process in which the file is read via the filesystem-in-userspacemodule.